Case-hardening compound and method of manufacturing



edective as energizers.

FATENT HUGH RODMAN, 0F OAKIVLONE, PENNSYLVANIA, ASSIGNOR T9 BUDMAN GHEMICAL COMPANY, OF VERONA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

CASE-HAEDENING COMPOUND AND METHOD OF MANUFACTURTNG}.

No Drawing.

a specification.

This invention relates to the art of manufacturing casehardening compounds. It discloses a new material for use in that art and a method of manufacturing a new and improved casehardening compound.

it is old to make a casehardening compound by coking a mixture of a coking substance and an energizing chemical so as to produce large masses of compound coke, which are then broken up and sized to meet conunercial requirements. The common practice of this special method consists in mixing ordinary coking coal with soda-ash and lime, all of these ingredients being in dry powdered condition, and then coking this mixture to produce a compound coke containing carbon and the reduced chemicals, this compound coke being subsequently crushed and screened to secure fragments about one-fourth inch in dimension. While a satisfactory casehardening material can be produced by this means, there are several difficulties involved.

One diiiiculty inherent in the use of coal as the coking agent in the method described above consists in the fact that all coals contain considerable ash, or inert material, which may react with the energizing chemicals, or directly with the steel being carbonizcd, to produce glassy adhesions upon the surface of the steel, this reaction being particularly noticeable when soda-ash is used as a chemical energizer.

Another difficulty consists in the actual loss of chemical energizer and the consequent reduction of the efficiency of the material, because of the fixing of the chemicals. by the ash in chemical combinations which are not For instance, the soda-ash may combine with the siliceous ash of the coal to produce alkali silicates; These are of little or no use as energizers.

Another difliculty is that the ordinary sulfur content of coking coal, usually above one per cent. of the weight of the coal, may pass to some extent and under conditions which Specification of Letters Patent. P t mm [W 29 192 Application filed June 28, 1920. Serial No. 392,412.

are not Well understood, into the steel, with the carbon. That is harmful.

Another difliculty consists in the fact that when these large masses of compound coke are crushed there is produced in the crushing operation considerable quantities, generally more than twenty-five per cent. of unmerchan-table fine particles and dust, which must be rejected and lost, orelse worked up by expensive methods into other products. As explained, coal has been used in this special art, subject to the limitations described. It has also been proposed to mix chemical energizers with crude oil and distill to produce a compound coke for casehardening. While this latter proposal has probably not been commercially put into practice, such a method would undoubtedly have some of the same disadvantages that exist along with coal. F or example, the product would have a high ash and sulfur. content, and the difiiculties resulting therefrom would be the same as in the coal compound.

All of these difficulties are overcome by the present invention which consists in the use of the distillates derived from coal as the coking agent in the mixture, instead of the coal itself. Preferably I use the ordinary hard fuel pitch instead of other distillates from coal because there aregreat quantities of this material. produced for which under present conditions little or no market exists, this condition having become accentuated with the recent increase in byproduct coke ovens. Such pitch is available in abundance with an ash content of less than one per cent. and a fixed carbon content of fifty-five or sixty er cent. when eoked as herein described. his may be compared with the ordinary eight or ten per cent. of ash in coking coal and 'a fixed carbon content of about sixty-five per cent. in the, Pittsburgh coal area.

By mixing thev pitch. with the energizing chemicals in any convenient manner, and then coking this mixture, T secure a compound coke which has much greater mechanical strength than the similar product made from coal, and of considerably less weight per unit of volume. quality (low specific density) is of value, as the material is used by bulk, rather than by weight. The casehardening efficiency of the pitch base material is also greater than that This latter parts 0f the coal base material, because of the ab sence' of ash in the pitch.

Furthermore the dust and fine fragments produced in crushing the compound coke made from pitch, may be added to lowing batch of raw materials going to the coking ovens or stills without'reducing the mechanical strength df the coke produced.

In other Words I am able to re-use the unmerchantable fines andv dust by the simple means of recharging them into the still with subsequent raw batches, Without loss of mechanical strength in the 'coke produced; Whereas, if the fines and dust from a coal base compound coke are mixed in With subsequent raw batches, a very weak and unsalable casehardening materialis produced. Thus the chief difficulties inherent in the use of coking coal in this special artmay be overcome by using the cheap (and generally unmarketable) pitch instead of uncoked coking coal.

. Pitch is the hard, brittle product remaining after the lighter oils and chemicals have been removed from ordinarycoal tar, and is preferable because of its comparativecheapness and high fixed carbon ratio,-but other distillates of coal, as for example the raw tar, may also be used.

In the practice of my invention any sort of commercial coking apparatus may be used. The chemicals may be mixed with broken up pitch While all the ingredients are solid, then the mixture heated, forming a coked compound, that is'then crushed and screened to size. Or, the pitch, or other carbonaceous material may be melted, then the chemicals stirred into the liquid, then the mixture coked, etc. Or the carbonaceous element may be completely coked, crushed and screenech and then the chemicals added and uniformly distributed over the carbo: naceous bases, by some such process as described in U. S. Patent 949446. made excellent material each Way, using about seven parts of soda-ash and twelve parts of lime hydrate with one hundred of pitch; and I- have mixed the dust and fines resulting from crushing the comthe fol- I have pound coke so produced With a similar batch of raw materials and produced cokeof apparently the same strength as the first batch.

Other energizing chemicals .may be used.

or at least till the smoke producing distillates have been all given off. The gases may be either used as fuel for the heating furnace, or may be distilled and reused for other purposes.

I claim: 1. A casehardenmg compound comprising coked pitch.

2. A casehardening compound comprising coked pitch, and an energizing chemical.

3. A casehardening compound comprising coked mixture of pitch and an energizing chemical. i

4. The method of manufacturing a casehardeningcompound, comprising mixing energizing chemicals with a coal tar base, coking the mixture, crushing and-screening to size.

5. 'Ihe method of manufacturing a casehardening compound, comprising mixing energizing chemicals with pitch, coking the mixture, crushing and screening to size.

6. The method of manufacturing casehardening materials consisting in coking a coal tar base, crushing and screening it to size, and mixlng suitable energizing chemicals therewith.

7. The method of' manufacturing case hardening materials consisting 1n coking pitch, crushing and screening it to size, and

mixing suitable energizing chemicals therewith.

In testimony whereof I have hereunto set my hand. HUGH RODMAN.

WVitnesses:

Jo. BAILY BROWN, HOWARD S. SNIVELY. 

